Ultraterrestrial

One of the more famous ultraterrestrial stories (which isn't saying much) in US history was the incredibly odd case of the Montauk Project, which was supposedly a part of the Philadelphia Experiment's research into time travel. The story goes that researchers encountered things in the timestream. Not Buckaroo Banzai-style urchin thingies, but some sort of nasty humanoid "Beast."

Angels and Demons would probably be considered ultraterrestrials, as would any strange and mystical beings that supposedly originate in a reality slightly removed from our own.